The processing technologies involved in certain manufacturing fields employ deposition techniques that involve considerable waste. The ability to recover the constituent materials of the overspray minimizes the cost of waste disposal and reduces the amount of new materials. Recycling efforts in this area also help in preserving natural resources.
According to one illustrative embodiment, modern gas turbines, especially aircraft engines and power generation systems, must satisfy the highest demands with respect to reliability, power, efficiency, economy, and operating service life. In the development of aircraft engines and power generation systems, the material selection, the search for new suitable materials, as well as the search for new production methods, among other things, play an important role in meeting standards and satisfying the demand.
The use of coatings on components such as combustors, high pressure turbine blades, vanes and shrouds is increasing in commercial as well as military gas turbine engines. Such coatings enable the desirable performance characteristics and operating in certain harsh environmental conditions. In one example, a bond coating and a barrier coating are deposited on articles such as the aeroengine and industrial turbines.
Barrier coatings in some applications are comprised of a material, such as yttria stabilized zirconia, that is applied to the various aircraft engine and gas turbine combustion components. In order to achieve good adhesion between the base metal and the barrier coating, a bond coat is typically applied to the base material. The barrier coating is then applied to the bond coat. The coating layers are applied such as by using high velocity oxy-fuel (HVOF) and/or plasma spray techniques, where powdered bond coating and barrier coating are propelled at high velocity under high temperature in a sheath gas at the part to be coated. Since coating booths are used for multiple bond coating and barrier coating chemistries interchangeably, all these materials (and other contaminants) become comingled as overspray. These powders are expensive and the overspray materials require costly disposal.
The HVOF and plasma spray processes tend to be very inefficient when one combines the natural spray efficiency with the component motion that often works on and off the part to be coated, and only a portion of the bond coating or barrier coating is coated on the part. During the deposition of the barrier coat and the bond coat on the article, the process inevitably involves overspray that does not become part of the article, and instead is overspray waste. Such overspray is generally comingled with other overspray waste materials. Recycling of the barrier coat and bond coat offer a significant cost savings, and eliminate disposal problems. Indeed, recovery of yttria or other rare earth element contained in the barrier coat, for example, has several advantages, including offsetting the need to purchase rare earth elements for thermal barrier coating manufacture as well as eliminating disposal considerations.
Presently, there is a need for new and improved methods to recycle waste overspray that comprises thermal barrier coat and/or bond coat (ceramic and metallic materials). Such new and useful methods and systems can permit less waste of costly raw materials used in the manufacture of articles used, for example, in aviation and energy-related manufacturing service shops. In particular, due to the value of the components that make up the thermal barrier coat and bond coat, any means to recoup and/or reduce the wastage of the thermal barrier coat and/or bond coat as a result of the application process would be of great value to industry.